lkml.org 
[lkml]   [2010]   [Mar]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] hangcheck-timer is broken on x86
On Sun, 28 Mar 2010 18:00:36 -0700
john stultz <johnstul@us.ibm.com> wrote:

> > 1) Does getrawmonotonic() satisfy hangcheck-timer? What I mean is, will
> > it always return the wallclock nanoseconds even in the face of CPU speed
> > changes, suspend, udelay, or any other suspension of kernel operation?
> > Yes, I know this is a tougher standard than rdtsc(), but this is what
> > hangcheck-timer wants. rdtsc() at least satisfied udelay and PCI hangs.
>
> getrawmonotonic() can be stalled and will wrap on some hardware (acpi pm
> timer wraps every 5 seconds).
>

I am not sure which archs do you mean. But in any case,
getrawmonotonic() is not just a wrap around a call to rdtsc() (or acpi
pm timer read). It is based on the clock->raw_time, which is updated
every timer interrupt by the update_wall_time(). So even if underlying
timer wraps, it doesn't lead to getrawmonotonic() returning 0 sec.


Y
[unhandled content-type:application/pgp-signature]
\
 
 \ /
  Last update: 2010-03-29 16:13    [W:1.590 / U:0.172 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site